This invention relates in general to workpiece clamping collets for use in multiple spindle lathes and in particular to a collet stop for positively positioning a workpiece within such a collet which is quickly and easily changeable with similar stops of varying size.
The multiple spindle lathe is a commonly known machine tool which is designed to support a plurality of workpieces simultaneously and to selectively remove material therefrom. To accomplish this, the spindle lathe is provided with a plurality of workpiece supporting spindles. Typically, four, six, or eight of such spindles are mounted in a circular array on a carrier assembly. The carrier assembly is rotatably supported on a frame of the spindle lathe. Means are provided for selectively rotating the carrier assembly so as to index each of the spindles through a plurality of operating positions.
At each of the carrier assembly operating positions, the spindles (and the workpieces supported therein) are aligned with one or more machine tools mounted on the spindle lathe. While so aligned, the machine tools are moved into engagement with the workpiece so as to remove material therefrom. When the material removal processes at each of the spindles are completed, the carrier assembly is indexed to the next operating position, where similar material removals occur. Thus, as a workpiece is sequentially indexed through each of the operating positions, material is removed therefrom to transform raw stock material into a finished workpiece.
In order to releasably engage and support the workpieces during the above-described machining process, each of the spindles is provided with a conventional clamping collet or chuck. The collet is opened to permit a finished workpiece to be removed and an unfinished workpiece to be inserted therein, and closed to engage the workpiece and and support it therein during machining at the various operating positions. A stop mechanism is usually provided on the spindle lathe for accurately positioning an unfinished workpiece axially within the collet before it is closed. Frequently, the stop mechanism (referred to as the collet stop) is located within the collet itself. Thus, when the collet is opened and the workpiece is inserted therein, the leading edge of the workpiece moves axially within the collet until it engages the collet stop. At that point, the collet is closed, thereby engaging and supporting the workpiece in a desired position relative to the collet.
Unfortunately, when the collet stop is located within the collet, it is difficult to gain access thereto. Such access is required when it is desired to change the relative position of the collet stop within the collet or to replace it with a differently sized collet stop. This changing of position or replacement of the collet stop is necessary when workpieces of different size or shape are to be machined on the spindle lathe. The lack of easy access causes the collet stop changeover operation to be tedious and time consuming, which is particularly significant if only small volumes of workpieces are to be machined. Known collet stops of this general type can require as much as forty minutes to complete a changeover operation. Thus, it would be desirable to provide an improved collet stop structure which can be changed in a quick and easy fashion.